Week 29 Blog- Gut-Brain Connection

What is the gut-brain axis- is a term used to refer to the two-way communication between your gastrointestinal tract and your central nervous system. The two organs (brain and gut) are connected both physically and biochemically in many ways.

In the walls of your digestive system (gut microbiome), researchers are understanding that there is a brain in your gut that links digestion, your mood, health and even the way you think. We have heard of the CNS- central nervous system- defined by Merriam- webster as - the part of the nervous system which consists of the brain and spinal cord, to which sensory impulses are transmitted and from which motor impulses pass out, and which coordinates the activity of the entire nervous system. 100 billion neurons in your brain and central nervous system (CNS) tell your body how to behave.

 This brain in your gut is called the enteric nervous system (ENS). The ENS is 2 thin layers of more than 100 million nerve cells lining your GI tract from your esophagus to your rectum. Jay Pasricha, M.D., director of the Johns Hopkins Center for Neurogastroenterology states about the ENS- “Its main role is controlling digestion, from swallowing to the release of enzymes that break down food to the control of blood flow that helps with nutrient absorption to elimination.”  “The enteric nervous system doesn’t seem capable of thought as we know it, but it communicates back and forth with our big brain—with profound results.” His research has found that the ENS may trigger big emotional shifts experienced by people coping with functional bowel problems such as constipation, diarrhea, bloating, pain and stomach upset. “For decades, researchers and doctors thought that anxiety and depression contributed to these problems. But our studies and others show that it may also be the other way around,” Pasricha says. Researchers are finding evidence that irritation in the gastrointestinal system may send signals to the central nervous system (CNS) that trigger mood changes. This two-way communication from gut to brain is giving answers to many important health concerns.


The gut-brain axis can be disrupted by many different factors, including stress and with an unhealthy gut microbiome (bacteria) in your digestive tract. When they are unhealthy, you are more susceptible to many health conditions. These include inflammation, metabolic syndrome, obesity, type 2 diabetes, depression or anxiety disorders, and neurodegenerative diseases such as Alzheimer’s disease or Parkinson’s disease. The Gut-Brain Axis has recently been called as the new “Central Nervous System”, which is a complex system of communication between the enteric nervous system in the gut and the central nervous system (CNS) in your brain. The gut contains over 500 million neurons which are connected to your brain through nerves in your nervous system.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845678/      The vagus nerve is one of the largest nerves in the body and it connects your gut and brain. Here is a little anatomy for you- The vagus nerve (also known as the 10th cranial nerve) is a very long nerve that originates in the brain stem and extends down through the neck and into the chest and abdomen. There are actually two vagus nerves (the left and the right),  but doctors usually refer to them together as “the vagus nerve.” It helps control several muscles of the throat and of the voicebox. It plays a major role in regulating the heart rate and keeping the gastrointestinal tract in working order. The vagus nerves also carry sensory information from the internal organs back to the brain. It sends signals in both directions.  https://pubmed.ncbi.nlm.nih.gov/29467611/

An interesting study in mice found that feeding them a probiotic reduced the amount of stress hormone in their blood. However, when their vagus nerve was cut, the probiotic had no effect. https://pubmed.ncbi.nlm.nih.gov/21876150/

This suggests that the vagus nerve is important in the gut-brain axis, its role in stress and many other roles.

Evidence to support having a healthy gut microbiota-

The Gut-Brain Axis is a two-way street, and both of these ‘roads’ are connected. When one road is in bad condition it affects the other road as well. When the Gut-Brain Axis is not functioning properly, this disfunction can lead to a range of problems including inflammation, depression, anxiety, and stress-related disorders. Let’s look at some evidence:

1. Gut bacteria are responsible for maintaining the Gut-Brain Axis by producing neurotransmitters that can stimulate specific cells in the gut to send signals back to the brain through various neurological pathways. Your gut and brain are also connected through chemicals called neurotransmitters. Neurotransmitters produced in the brain control feelings and emotions. For example, the neurotransmitter serotonin contributes to feelings of happiness and also helps control your body clock. A large proportion of serotonin is produced in the gut. Many other neurotransmitters are also produced by your gut cells and also the trillions of microbes living there. Your gut microbes also produce a neurotransmitter called gamma-aminobutyric acid (GABA), which helps control feelings of fear and anxiety. Studies in laboratory mice have shown that certain probiotics can increase the production of GABA and reduce anxiety and depression-like behavior. https://pubmed.ncbi.nlm.nih.gov/26577887/  

2. Besides serotonin and GABA, the trillions of microbes that live in your gut also make other chemicals that affect how your brain works. Your gut microbes produce lots of short-chain fatty acids. They make SCFA by digesting fiber. SCFA affect brain function in a number of ways, such as helping to reduce appetite. One of these SCFA, butyrate, and the microbes that produce it are also important for forming the barrier between the brain and the blood, which is called the blood-brain barrier. More anatomy- The blood-brain barrier is made up of tightly packed cells in the brain’s capillaries that prevent harmful substances from entering the brain. It protects your brain from injury and disease while also letting in substances that your brain needs, like oxygen and water.  Gut microbes also metabolize bile acids and amino acids to produce other chemicals that affect the brain. Bile acids are chemicals made by the liver that are normally involved in absorbing dietary fats. However, they may also affect the brain. Two studies in mice found that stress and social disorders reduce the production of bile acids by gut bacteria and alter the genes involved in their production. https://pubmed.ncbi.nlm.nih.gov/27006086/         https://pubmed.ncbi.nlm.nih.gov/28965876/      

3. Your gut-brain axis is also connected through the immune system. Gut and gut microbes play an important role in your immune system and inflammation by controlling what is passed into the body and what is excreted. If your immune system is running on high gear for too long, it can lead to inflammation. This has been associated with a number of brain disorders like depression and Alzheimer’s disease. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1760754/

Lipopolysaccharide (LPS) is an inflammatory toxin made by certain bacteria. It will cause inflammation if too much of it passes from the gut into the blood. When the gut barrier becomes leaky, bacteria and LPS cross over into the blood and this has been associated with a number of brain disorders including severe depression, dementia and schizophrenia.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4604320/        This is just a sampling of evidence on the power of your gut microbiome.

Three weeks ago, the RefineMEnt podcast was on fueling for brain health. Go back to refresh for we are now moving to:

What can we do with our diet to aid the gut-brain axis?

Diet is one of the most important factors of the gut-brain axis. To improve your Gut-Brain Axis try following these tips to get back on track. 1.Get enough fiber in your diet from fruits and vegetables. The Mediterranean diet, which is characterized by a high fruit and vegetable intake, healthy fats such as olive oil and fish, wholegrains, legumes and nuts has been shown to increase the diversity of gut microbiota, which has a direct impact on the gut-brain axis.  2. get rid of the bad bacteria’s and yeast with beneficial bacteria (prebiotic, probiotic, postbiotic food or supplements) see my 3-part gut microbiome podcast series.  3. Add fermented food- remember to join Sheri’s kombucha club- ¼ cup twice a day 4. Get rid of added sugars and sugary food and drinks 5. reduce stress as much as possible 6. exercise MOVE regularly 7. get adequate sleep and rest 8. Consult your health care provider for other options if you have a specific health need.

Research is still underway on how to improve the balance of gut microbiota to positively affect the gut-brain axis. Gut microbiome therapy may be used in some future medical therapies for psychiatric disorders, autism, and neurodegenerative disease. https://ifho.org/gut-brain-axis/     


One of the most cutting-edge areas of research involves the ‘gut-brain axis’ – the connection between the brain, gut, and microbiome and its potentially huge influence over our health. The gut microbiome has trillions of microorganisms that mainly live in the gut. Those microorganisms are mainly comprised of bacteria, and it is these microbes that reside in the gut that directly communicate from the gut to the brain via the vagus nerve. Together, the gut-brain axis is a complex interconnected two-way street. This means that when an issue arises at any point within these communication loops, it can affect the whole system. Only recently have scientists started to better understand the gut-brain axis and how it can impact not only physical and digestive issues, such as irritable bowel syndrome (IBS), mental health conditions like depression and anxiety and neurodegenerative diseases such as Alzheimer’s disease or Parkinson’s disease.

The link between the gut, brain, microbiome and our health are undeniable. By feeding your body and gut microbiome properly, you also are fueling your brain for a healthier you!